(1) Field of the Invention
The invention is related in general to wellsite surface equipment such as fracturing pumps and the like.
(2) Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98
Multiplex reciprocating pumps are generally used to pump high pressure fracturing fluids downhole. Typically, the pumps that are used for this purpose have plunger sizes varying from about 9.5 cm (3.75 in.) to about 16.5 cm (6.5 in.) in diameter. These pumps typically have two sections: (a) a power end, the motor assembly that drives the pump plungers (the driveline and transmission are parts of the power end); and (b) a fluid end, the pump container that holds and discharges pressurized fluid.
In triplex pumps, the fluid end has three fluid cylinders. For the purpose of this document, the middle of these three cylinders is referred to as the central cylinder, and the remaining two cylinders are referred to as side cylinders. Similarly, a quintuplex pump has five fluid cylinders, including a middle cylinder and four side cylinders. A fluid end may comprise a single block having cylinders bored therein, known in the art as a monoblock fluid end.
The pumping cycle of the fluid end is composed of two stages: (a) a suction cycle: During this part of the cycle a piston moves outward in a packing bore, thereby lowering the fluid pressure in the fluid end. As the fluid pressure becomes lower than the pressure of the fluid in a suction pipe (typically 2-3 times the atmospheric pressure, approximately 0.28 MPa (40 psi)), the suction valve opens and the fluid end is filled with pumping fluid; and (b) a discharge cycle: During this cycle, the plunger moves forward in the packing bore, thereby progressively increasing the fluid pressure in the pump and closing the suction valve. At a fluid pressure slightly higher than the line pressure (which can range from as low as 13.8 MPa (2 Ksi) to as high as 145 MPa (21 Ksi)) the discharge valve opens, and the high pressure fluid flows through the discharge pipe.
The power end typically includes an engine such as a diesel or gasoline engine, a transmission and a driveline that provides the motive force to reciprocate the pump plungers via rods which are known in the art as pony rods. Often the power ends and fluid ends from different manufacturers are incompatible due to the misalignment of the pony rods and plungers, as well as different profiles and bolting patterns of the attachment flange of the power end relative to the connection block on the fluid end. Power ends may be produced by various manufacturers with considerable variability in the design and/or dimensions of the attachment flange, pony rods, driveline, etc., both between manufacturers as well as between different models from the same manufacturer.
Given a pumping frequency of 2 Hz, i.e., 2 pressure cycles per second, the fluid end body can experience a very large number of stress cycles within a relatively short operational lifespan. These stress cycles, together with the high operating pressures, the difficult nature of the fluids being pumped, and often extreme environmental conditions, gives rise to high maintenance requirements both on the fluid end as well as the power end.
Frequently it is desired to remove power end and/or fluid end pump assembly components from a working pump and replace them with components from inventory to keep the pump assembly in operation while the removed component can be repaired and returned to inventory; however, there are substantial differences between different pump assembly makes and models such that a relatively large inventory is required to provide suitable replacement power ends and/or fluid ends for every type an enterprise may have in operation. A power end from one manufacturer, for example, may not have the proper orientation of drive rods and tie rods to the fluid end of another manufacturer, or the appropriate stroke length. Standardization of fluid ends and pump ends for one manufacturer can lead to sourcing and pricing issues and for these reasons it is advantageous to have a wide range of suppliers for the various pump components.
It remains desirable to provide improvements in wellsite surface equipment in efficiency, flexibility, reliability, and maintainability.